Swing-type actuator

ABSTRACT

A swing-type actuator includes a coil, at least one arm and a thermoplastic body joining the coil and the arm. In one embodiment, the arm is preferably a generally planar aluminum stamping having an opening to which the read/write head may be mounted at one end thereof. A feature is located in the opposite end of the arm to facilitate attachment to the thermoplastic body. The arm also includes at least one flat side perpendicular to its plane at the end including the notch. The body is molded around a portion of the arm and cooperates with the feature to secure the arm thereto. The body also overlaps part of the coil and surrounds the outer circumference thereof. A journal is formed in the body for receiving a shaft on which the actuator pivotally rotates. A grounding pin extending through the arm prevents static charge build-up. Alternatively, a portion of the arm may extend into the journal to contact the bearing. According to another embodiment of the present invention, the arm includes a plastic portion and a metal mounting pad. The plastic portion is molded around a securement portion of the mounting pad to form the arm. The body is then molded around portions of the arm and the coil in the same manner as the first embodiment of the invention. The plastic portion of the arm is preferably formed of electrically conductive material and is provided with a grounding pin to facilitate discharging of static charge.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to swing-type actuators for positioningread/write heads in memory storage devices and, more particularly, to animproved swing-type actuator constructed partially from plastic.

Numerous swing-type actuators are known in the prior art. Representativeexamples include those shown in U.S. Pat. No. 4,985,652 to Oudet, et al.and U.S. Pat. No. 4,916,456 to Manzke, et al. Such devices typicallyinclude a coil secured to one or more longitudinally extending arms. Ifmore than one arm is utilized, the plurality of arms is known as an"E-block". A read/write head is typically attached to each arm on theend opposite the coil. The actuator is pivotally secured about a shaftsuch that the read/write head is positioned adjacent a data disk and thecoil is placed in a magnetic field by, for example, positioning itadjacent one or more permanent magnets. Current is supplied to the coil,thereby generating an electromagnetic force and causing movement of thecoil within the preexisting magnetic field. Correspondingly, the armspivot about the shaft to move the read/write heads to selected locationsadjacent the disk.

In some embodiments of the above-described swing-type actuator, the armis constructed from metal, such as aluminum. Metal arms have severaladvantages, including the ability to more readily and securely attachread/write heads to the arm, the ability to maintain exacting tolerancesfor the arm, and the relative ability to more easily machine featuresinto the arm. The coil is typically attached to metal arms by means ofscrews, similar fasteners or adhesives. However, for various reasons,including ease of manufacturing, it has been found desirable to securethe coil to the arm by injection molding thermoplastic material around aportion of the coil and a portion of the arm. Examples of such actuatorsinclude U.S. Pat. No. 5,122,703 to Takahashi, et al., as well asnumerous earlier actuators manufactured by the assignee of the presentapplication.

Although the above-described actuators are all acceptable for theirintended uses, they do have certain undesirable features. For example,an aluminum E-block can be relatively expensive to manufacture.Additionally, it may be desirable to provide an actuator having a loweroverall weight than one utilizing an aluminum E-block, thereby reducinginertia and momentum and the attendant forces necessary to move and stopthe actuator. Accordingly, all-plastic actuators have been proposed. Insuch actuators, the coil is placed in a mold and the actuator arm issimultaneously formed from a thermoplastic material and molded to thecoil. Examples of such actuators include U.S. Pat. No. 5,165,090 toTakahashi, et al., as well as earlier actuators manufactured by theassignee of the present application.

Although all-plastic actuators may be suitable for their intendedpurpose, they lack some of the more desirable properties of actuatorshaving metal arms. For example, it has been determined that theread/write head may be more easily and readily attached to a metalcomponent than a plastic one. Similarly, it may be easier to machinefeatures into metal than plastic.

Accordingly, it is an object of the present invention to provide animproved swing-type actuator for carrying a read/write head.

Another object of the present invention is the provision of a swing-typeactuator that is lightweight and durable.

Yet another object of the present invention is the provision of aswing-type actuator that allows for easy and secure attachment of theread/write head to the actuator arm.

Another object of the present invention is the provision of a swing-typeactuator that can have a read/write head secured thereto with a stakingball and eyelet combination.

Still another object of the present invention is the provision of aswing-type actuator having an arm capable of being machined to includedesired features.

These and other objects of the present invention are attained by theprovision of a swing-type actuator which comprises a coil, at least onearm formed from metal and having a first end and a second end, and amolded thermoplastic body which includes a journal disposed between thefirst end of the arm and the coil. The body is molded about a portion ofthe first end of the arm and at least a portion of the coil so as tosecure the arm and coil to the body.

In one embodiment of the present invention, the arm is a stamping havinga generally flat portion of uniform thickness and at least one flatsurface on one edge thereof. The molded body surrounds a portion of theflat surface. One end of the arm includes a feature that cooperates witha portion of the body to secure the arm to the body, and the other endof the arm has a hole therein for attaching a read/write head to thearm. The arm includes at least one wire guide machined therein forreceiving a wire which attaches to the read/write head.

In another embodiment of the present invention, the arm includes a holetherein for reducing the mass of the arm.

In another embodiment of the present invention, the actuator includes abobbin having a body, a plurality of terminal pin sleeves havingterminal pins disposed therein and a bridge member joining the body andthe sleeves. The coil includes a plurality of lead wires attached to theterminal pins and the coil is disposed about the body of the bobbin.

According to yet another embodiment of the present invention, aswing-type actuator includes a coil, at least one arm and a moldedthermoplastic body. The arm includes first and second ends and comprisesa plastic portion and a metal mounting pad. The body has a first portionmolded about a portion of the coil to join the coil to the body, and asecond portion molded about the first end of the arm to join it to thebody.

In still another embodiment of the present invention, the mounting padincludes a body portion, a securement portion for securing the mountingpad to the plastic portion and an attachment portion for attaching aread/write head to the mounting pad. The attachment portion includes ahole therein for attaching a read/write head to the mounting pad and hasbeveled edges for accommodating the tooling used to attach theread/write head to the mounting pad. Both the attachment portion and thesecurement portion extend generally perpendicularly from the body. Theplastic portion surrounds the securement portion so as to secure themounting pad to the plastic portion. Additionally, the plastic portionis electrically conductive.

According to another embodiment of the invention, the plastic portion ofthe arm includes at least one wire guide. The wire guide may take theform of staggered protrusions extending from the plastic portion.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a swing-type actuator according to thepresent invention.

FIG. 2 shows a cross-sectional view taken along line 2--2 in FIG. 1.

FIG. 3 is a top plan view of an embodiment of an arm used in conjunctionwith the actuator shown in FIG. 1.

FIG. 4 is a side plan view of the arm of FIG. 3.

FIG. 5 is a top plan view of an alternative embodiment of a swing-typeactuator according to the present invention.

FIG. 6 is a partial, top plan view of another embodiment of a swing-typeactuator according to the present invention.

FIG. 7 is a cross-sectional view taken along line 7--7 of in FIG. 6.

FIG. 8 is another alternative embodiment of an arm for use inconjunction with a swing-type actuator according to the presentinvention.

FIG. 9 is an end view of a mounting pad which is a component of the armshown in FIG. 8.

FIG. 10 is a partial cut-away side plan view of the arm shown in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a top plan view of a swing-type actuator 10 according tothe present invention. Actuator 10 comprises coil 20, bobbin 30, arms 40and body 50. Coil 20 has an inner circumference 22 and an outercircumference 24. Coil 20 is formed by winding wires, preferablyresin-coated copper, around a mandrel. Coil 20 may then be press-fitaround bobbin 30, as described in co-pending U.S. patent applicationSer. No. 08/243,476 filed on May 16, 1994, the disclosure of which ishereby incorporated by reference. Bobbin 30 includes body 32, bridgemember 34, and terminal pin sleeves 36. Bridge member 34 extendsupwardly and behind body 32 and joins body 32 to terminal pin sleeves36. Bridge member 34 can be better seen in FIG. 2. Two terminal pins 38are secured in bobbin terminal pin sleeves 36. Bobbin 30 is preferablymolded from a thermoplastic material. After positioning coil 20 aroundbobbin 30, the free ends of coil 20 are secured to terminal pins 38.Current may be supplied to coil 20 via terminal pins 38, as is commonlyknown in the art. A tang 60 extends from one end of coil 20. Tang 60interacts with a stop member to limit the angular displacement ofactuator 10.

Arms 40 are generally flat members of uniform thickness having first end41 and second end 42. Each arm 40 has an opening 43 in first end 41.Read/write heads may be attached to arms 40 via openings 43 in a mannercommonly known in the industry. Arms 40 further include a feature 44 insecond end 42. Feature 44 is shown as a notch for purposes of example.Two flat surfaces 46 and 48 are formed on each edge of second end 42.Flat surfaces 46 and 48 assist in properly aligning arms 40 in a moldduring the formation of body 50, described below. Arms 40 furtherinclude wire guides 49 on one side thereof (FIG. 4). Wire guides 49provide a track for wires running to the read/write heads. Each arm 40also includes a hole 40A that receives a conductive pin 40B via aninterference fit. Pin 40B is used to ground arms 40, as described below.

Arms 40 may be formed by stamping from a sheet of aluminum and thenmachining wire guides 49 into the sides. This method of manufacturingarms 40 has the advantage of being relatively inexpensive when comparedto the cost of an aluminum E-block. Thus, by eliminating the E-blockcompletely, the present invention results in a significant cost savings.Alternatively, arms 40 may be stamped from a sheet of magnesium.Magnesium has lower mass than aluminum and, therefore, results in anactuator with lower inertial mass.

FIG. 5 shows an alternative embodiment of arm 40. Due to the degree ofoverall similarity existing between the embodiments of FIGS. 3 and 5,like reference numerals are used for corresponding structures in eachfigure. In this embodiment, a hole 40C is formed in arm 40. The presenceof hole 40C reduces the amount of material comprising arm 40.Accordingly, the inertial mass of actuator 10 is also reduced. Hole 40Cmay be of any size desired, so long as it is not made so large as toreduce the structural integrity of arm 40.

Body 50 includes journal 52 for receiving a cartridge bearing assemblyabout which actuator 10 rotates. Body 50 further includes an arm joiningportion 54 surrounding second end 42 of arm 40. Arm joining portion 54also fills notch 44 in arm 40 to further assist in securing arm 40 tobody 50. Body 50 also includes coil joining portion 56. Coil joiningportion 56 includes peripheral portion 58 surrounding coil 20. As isknown in the industry, a tang 60 may be provided on actuator 10. If so,tang securement portion 59 is integrally formed with peripheral portion58 and secures tang 60 to coil 20.

To assemble actuator 10, coil 20, bobbin 30, tang 60 and second end 42of arms 40 are inserted into a mold. A thermoplastic material is theninjected into the mold to form body 50. During the injection process,arm joining portion 54 and coil joining portion 56 of body 50 areformed. These features may be more clearly seen in FIG. 2. As shown inthat figure, arm joining portion 54 surrounds second end 42 of each arm40. Additionally, arm joining portion 54 fills feature 44 of each arm40, thereby providing better bonding. Similarly, coil joining portion 56overlaps coil 20 and bobbin 30 just beyond bridge member 34 of bobbin30. Peripheral portion 58 is also formed around coil 20 during themolding process. Additionally, tang securement portion 59 surrounds aportion of tang 50 and secures it to coil 20. An extended portion of pin40B is folded over the top arm 40 and secured to the ground pad of acircuit board (not shown) attached to the side of actuator 10, as iscommonly known in the art. This prevents the build up of static chargeon arms 40, which can result from the spinning of the magnetic discs.

FIG. 6 shows a partial top plan view of another embodiment of aswing-type actuator according to the present invention. Again, likereference numerals have been used for corresponding structures betweenthis embodiment and those shown in FIGS. 3 and 5. This embodimentutilizes an alternative grounding method. In this embodiment, second end42 of arm 40 is extended beyond journal 52 of body 50. Each arm 40 isprovided with an opening. Arms 40 are placed in a mold with the othercomponents of actuator 10 and body 50 is molded such that journal 52 isconcentric with the openings in arms 40. Journal 52 and the openings inarms 40 are then drilled out to the desired diameter. In this manner, aportion of each arm 40 is exposed in journal 52. This can be seen inFIG. 7. When actuator 10 is placed on the cartridge bearing assembly,the exposed portions of arms 40 will contact the bearing assembly. Inthis manner, arms 40 are grounded through contact with the bearing.

Actuator 10 of the present invention operates in basically the samemanner as the prior art actuators described above. Specifically, journal52 of body 50 is placed over a shaft about which actuator 10 may rotate.Coil 20 is placed in a magnetic field and arms 40, with read/write headsattached thereto via openings 43, are positioned such that theread/write heads are disposed adjacent data disks. Wires lead from theread/write heads to a circuit board attached to the side of actuator 10,as is known in the art. The wires are disposed in wire guides 49 andsecured with adhesive. Current is supplied to coil 20 via terminal pins38, thereby causing rotation of actuator 10 as previously described. Inthis manner, the read/write head is positioned on the computer disk.

An alternative embodiment of the arm is shown in FIGS. 8 through 10 andis indicated by reference number 140. In this embodiment, arm 140comprises plastic portion 70 and mounting pad 80. Plastic portion 70includes an end 72, which forms the first end of arm 140. Plasticportion 70 further includes feature 74 and flat sides 76 and 78. Feature74 and flat sides 76 and 78 correspond to feature 44 and flat sides 46and 48 in the previously described embodiments of arm 40.

Mounting pad 80 comprises base 82, attachment portion 84, and securementportion 85. Attachment portion 84 includes a hole 83 therein formounting a read/write head to mounting pad 80 in a manner commonly knownin the industry. Attachment portion 84 further includes beveled edges85, which accommodate the tooling utilized to remove a read/write headfrom arm 140, if necessary. Securement portion 85 extends from base 82on a side opposite attachment portion 83. In the embodiment shown,securement portion 85 is a generally T-shaped member that is thinner andnarrower than base 82. Securement portion 85 is used to secure mountingpad 80 to plastic portion 70 as described below. Mounting pad 80 ispreferably formed form aluminum or magnesium.

To form the arm 140, mounting pad 80 is placed in a mold and the mold isinjected with plastic to form plastic portion 70. As plastic portion 70is formed, the plastic surrounds securement portion 85 of mounting pad80, thereby providing better attachment of mounting pad 80 to plasticportion 70. Note that it is not necessary that securement portion 85 beT-shaped. Rather, any of a number of shapes may be utilized that providea protrusion on mounting pad 80 around which plastic portion 70 may beformed.

To prevent build up of the static charge on arm 140, the plastic used tomold plastic portion 70 is preferably a glass and carbon reinforcedthermoplastic. The presence of the carbon makes the plastic conductive.Thus, plastic portion 70 may be grounded in the same manner as the allmetal embodiments of arm 40.

To form an actuator 10 utilizing arm 140, coil 20, bobbin 30, tang 60and arm 140 are placed into the same type of mold used in conjunctionwith arm 40 and body 50 is formed in the same manner as described above.Alternatively, arm 140 could be molded at the same time body 50 isformed. However, molding arm 140 separately allows utilization of lesscomplex molds. This is particularly true because unlike plastic portion70 of arm 140, body 50 is formed from a nonconductive plastic. This isnecessary since, to do otherwise, would short out the terminal pins ofthe coil. Thus, molding arm 140 at the same time as body 50 wouldrequire injecting different portions of the mold with differentplastics. Alternatively, bobbin 30 and terminal pin sleeves 36 can beformed such that terminal pins 38 are isolated from body 50 by thenonconductive bobbin. If so, the same conductive plastic could be usedto form body 50 and plastic portion 70. Arms 140 would then be groundedthrough contact between journal 52 and the bearing on which it pivots.The insulation on the wires that form coil 20 shield coil 20 from theconductive plastic.

Although not shown in FIGS. 8 through 10, arm 140 may be provided withmachined wire guides similar to wire guides 49 in arm 40. Alternatively,plastic portion 70 of arm 140 may be provided with wire guides in theform of a plurality of protrusions 79 extending therefrom. Protrusions79 have a dove tail configuration which helps prevent the formation offlash during the molding process. Protrusions 79 are spaced apartvertically such that a wire running from the read/write head may bedisposed above the lower protrusions 79 and below the upper protrusions79. The wire may be secured with adhesive. Similarly, arm 40 could beprovided with wire guides in the form of protrusions. Such protrusionscould be formed during stamping.

Although the present invention has been described and illustrated indetail, it is to be clearly understood that the same is by way ofillustration and example only and is not to be taken by way oflimitation. Numerous variations may be made to the embodiment describedabove without departing from the invention. For example, the number ofarms 40 may be varied. Similarly, the configuration of feature 44 may bedifferent from that shown. For example, feature 44 could also bereplaced with one or more protrusions extending from the surface of arm40 to provide a location for increased bonding with arm joining portion54. This may be particularly advantageous because most thermoplasticsshrink as they set. Thus, arm joining portion 54 would firmly grip suchprotrusions. Also, the length of arms 40, as well as the relative sizesof arms 40 and body 50, may be varied. Furthermore, although in theabove described embodiment coil 20 is wound separately on a mandrel andpositioned around bobbin 30, coil 20 could alternatively be wounddirectly on bobbin 30. Accordingly, the spirit and scope of theinvention are to be limited only by the claims appended hereto.

What is claimed is:
 1. A swing-type actuator, comprising:a coil; an armfor carrying a read/write head, said arm being formed from metal andhaving a first end and a second end; and a molded thermoplastic body,said body including a journal disposed between said first end of saidarm and said coil, wherein said body is molded about a portion of saidfirst end of said arm and at least a portion of said coil so as tosecure said arm and said coil to said body.
 2. The actuator according toclaim 1, wherein said first end of said arm includes a feature thatcooperates with a portion of said body to secure said arm to said body.3. The actuator according to claim 2, wherein said arm includes agenerally flat portion of uniform thickness extending between said firstand second ends.
 4. The actuator according to claim 1, wherein said armincludes at least one flat surface on one edge of said arm for aligningsaid arm in a mold.
 5. The actuator according to claim 4, wherein saidbody surrounds a portion of said flat surface.
 6. The actuator accordingto claim 1, wherein said arm is a stamping.
 7. The actuator according toclaim 6, further comprising means formed on said arm for attaching aread/write head to said arm.
 8. The actuator according to claim 7,wherein said means for attaching a read/write head includes a holeextending through said arm.
 9. The actuator according to claim 1,wherein said arm includes at least one wire guide formed therein forreceiving a wire which attaches to the read/write head.
 10. The actuatoraccording to claim 1, further comprising a bobbin having a body, aplurality of terminal pin sleeves having terminal pins disposed thereinand a bridge member joining said bobbin body and said sleeves.
 11. Theactuator according to claim 10, wherein said coil includes a pluralityof lead wires attached to said terminal pins and said coil is disposedabout said bobbin body.
 12. The actuator according to claim 1, furthercomprising a grounding pin, and wherein said arm includes a hole forreceiving said grounding pin.
 13. The actuator according to claim 12,wherein said grounding pin extends through said arm and outwardly fromsaid body.
 14. The actuator according to claim 12, further comprising atleast two arms and wherein said grounding pin connects said arms toground.
 15. The actuator according to claim 1, wherein a portion of saidarm is exposed within said journal.
 16. The actuator according to claim15, wherein said arms are connected to ground through contact with abearing disposed in said journal.
 17. A swing-type actuator,comprising:a coil; an arm for carrying a read/write head, said armhaving first and second ends and comprising a plastic portion and ametal mounting pad; and a molded thermoplastic body having a firstportion molded about a portion of said coil to join said coil to saidbody, and having a second portion molded about said first end of saidarm to join said arm to said body.
 18. The actuator according to claim17, wherein said mounting pad includes a base, a securement portion forsecuring said mounting pad to said plastic portion and an attachmentportion for attaching a read/write head to said mounting pad.
 19. Theactuator according to claim 18, wherein said attachment portion includesmeans for attaching a read/write head to said mounting pad.
 20. Theactuator according to claim 19, wherein said means for attaching aread/write head to said mounting pad includes a hole in said attachmentportion.
 21. The actuator according to claim 20, wherein said attachmentportion includes beveled edges.
 22. The actuator according to claim 19,wherein said attachment portion extends generally perpendicularly fromsaid base.
 23. The actuator according to claim 18, wherein saidsecurement portion extends generally perpendicularly from said base. 24.The actuator according to claim 18, wherein said plastic portionsurrounds said securement portion so as to secure said mounting pad tosaid plastic portion.
 25. The actuator according to claim 18, whereinsaid securement portion is thinner than said base.
 26. The actuatoraccording to claim 25, wherein said securement portion is narrower thansaid base.
 27. The actuator according to claim 26, wherein saidsecurement portion is generally T-shaped.
 28. The actuator according toclaim 17, wherein said plastic portion is electrically conductive. 29.The actuator according to claim 28, further comprising a grounding pin,and wherein said plastic portion includes a hole for receiving saidgrounding pin.
 30. The actuator according to claim 29, wherein saidgrounding pin extends through said arm and outwardly from said body. 31.The actuator according to claim 29, further comprising at least two armsand wherein said grounding pin connects said arms to ground.
 32. Theactuator according to claim 28, wherein said body includes a journal anda segment of said plastic portion is exposed within said journal. 33.The actuator according to claim 32, wherein said arms are connected toground through contact with a bearing disposed in said journal.
 34. Theactuator according to claim 28, wherein said plastic portion is formedfrom glass and carbon reinforced thermoplastic material.
 35. Theactuator according to claim 17, wherein said arm includes at least onewire guide for receiving a wire which attaches to the read/write head.36. The actuator according to claim 35, wherein said wire guidecomprises a plurality of staggered protrusions extending from said arm.37. The actuator according to claim 17, wherein one end of said armincludes a feature that cooperates with a portion of said body to securesaid arm to said body.
 38. The actuator according to claim 17, whereinsaid arm includes a generally flat portion of uniform thicknessextending between said first and second ends.
 39. The actuator accordingto claim 17, wherein said arm includes at least one flat surface on oneedge of said arm for aligning said arm in a mold.
 40. A swing-typeactuator, comprising:a coil; an arm for carrying a read/write head, saidarm having first and second ends and comprising a plastic portion and ametal mounting pad; a molded thermoplastic body having a first portionmolded about a portion of said coil to join said coil to said body, andhaving a second portion molded about said first end of said arm to joinsaid arm to said body; and a bobbin having a body, a plurality ofterminal pin sleeves having terminal pins disposed therein and a bridgemember joining said bobbin body and said sleeves.
 41. The actuatoraccording to claim 40, wherein said coil includes a plurality of leadwires attached to said terminal pins and said coil is disposed aboutsaid bobbin body.
 42. The actuator according to claim 41, wherein saidbody and said plastic portion are electrically conductive, and saidbobbin insulates said terminal pins from said body and said plasticportion.
 43. The actuator according to claim 42, wherein said bodyincludes a journal and said arms are connected to ground through contactbetween said journal and a bearing disposed in said journal.
 44. Theactuator according to claim 17, wherein said body includes a journal onwhich said actuator pivotally rotates.
 45. The actuator according toclaim 44, wherein said body and said plastic portion are electricallyconductive and said arms are connected to ground through contact betweensaid journal and a bearing disposed in said journal.
 46. A swing-typeactuator, comprising:a coil; an arm for carrying a read/write head, saidarm having first and second ends and comprising a plastic portion and ametal mounting pad; and a body joining said coil to the first end ofsaid arm.
 47. The actuator according to claim 46, wherein the bodyincludes a journal disposed between said coil and said arm.
 48. Theactuator according to claim 47, wherein said plastic portion of the armand said body are molded from thermoplastic material.
 49. The actuatoraccording to claim 48, wherein said plastic portion of the arm is formedfrom an electrically conductive thermoplastic material.